The USB is a cable bus that supports data exchange between a host computer (USB host) and a wide range of simultaneously accessible peripherals (USB devices). The USB physical interconnect is a tiered star topology. A hub is at the center of each star. Each wire segment is a point-to-point connection between the USB host and a hub or a USB device, or a hub connected to another hub or USB device. FIG. 1 illustrates the topology of the USB.
The USB host contains host controllers that provide access to the USB devices in the system. The host controller performs several duties with regard to the USB and its attached USB devices. These duties include reporting and managing the states of the USB devices, converting protocol and data information between a native format and a bit stream transmitted on the USB, frame generation, processing requests for data transmission, and transmission error handling. The USB specification requires that a round trip response time delay for transmissions between a host controller and a USB device be within a specified time of 18 bit times. All transmissions on the USB are performed as packets within a transaction. A USB device must receive a transmission of a packet from the host controller and send a response packet back to the host controller within a specified time. This specified time only applies to packets within the transaction. This allows the USB system to preserve timing on the bus at the 12 Mbs rate and to support USB devices having real time requirements. A host controller expecting a response to a transaction will invalidate the transaction if it does not see a start of packet transition (SOP) within the time-out period after the end of the first packet's transmission.
The round trip response time delay requirements for USB systems make it difficult to implement a wireless link for configuring a wireless module onto a USB system. Additional time is required for transforming wire data through a transceiver to wireless data, transmitting the wireless data between a system side module and a remote module, and transforming the wireless data back to wire data. Current technologies for transmitting wireless signals such as infrared signals, radio signals, ultrasonic wave signals, and other aerial propagation signals do not provide the adequate bandwidth for transmitting data signals on the USB while complying with the round trip response time delay requirement.
Thus, what is needed is a method and apparatus for configuring a wireless module for connecting USB devices onto a USB system implementing the current technologies for transmitting wireless signals.